A structure having a resin coating layer provided on an outermost surface of a bearing alloy layer is known to be effective as a structure for improving slide bearing characteristics. There is proposed a slide bearing as one example of the above structure (See Patent Document 1: JP-A-2004-211859), in which an overlay layer containing molybdenum disulfide (MoS2) as a solid lubricant and a PAI resin (polyamide-imide resin) as a binder resin is formed on a flattened surface of the bearing alloy layer. The overlay layer has a helical groove and annular projections formed, as a recess-and-protrusion shape, on the surface thereof. In the slide bearing, the regularly-formed recess-and-protrusion shape on the surface of the overlay layer can maintain lubricating oil in the recess parts of the recess-and-protrusion shape. Therefore, improvement of seizure resistance can be expected.
The slide bearing described in Patent Document 1 is intended to improve its conformability to a rotation shaft through plastic deformation of the overlay layer (see paragraph 0006 of Patent Document 1). However, it can be difficult for the overlay layer to be plastically deformed because the overlay layer is made of a synthetic resin and has high elasticity. Therefore, it can take a long time before the conformity is achieved. It may be also assumed that abrasion of the overlay layer achieves the conformity to the rotation shaft. However, it can take a long time before adequate conformity is achieved by the abrasion of the overlay layer because the synthetic resin that constitutes the overlay layer has a low friction property.
Examples of techniques focusing on the above problem include a technique described in Patent Document 2: JP-A-2011-179566. In the technique, the slide bearing has a bearing alloy layer having annular grooves and crests formed thereon and has an overlay layer made of a low-friction synthetic resin that covers a surface of the bearing alloy layer. The surface of the overlay layer is formed as a recess-and-protrusion surface to match a recess-and-protrusion surface of the bearing alloy layer. Because the crests are provided to the bearing alloy layer as above, the crests of the bearing alloy layer are expected to be plastically deformed when a load is applied to the slide bearing from the rotation shaft. The above structure is intended to expedite the conformity of the bearing to the rotation shaft even in a configuration using the overlay layer made of a low-friction synthetic resin. In an experimental example described in Patent Document 2, the crests of the bearing alloy layer result in the plastic deformation despite the presence of the overlay layer made of the low-friction synthetic resin (see paragraph 0012 and FIG. 2 of Patent Document 2).
However, an experimental example described in Patent Document 2 assumes a condition that bearing contact pressure is 84 MPa (50 MPa in FIG. 3), which is close to limit contact pressure performance of general aluminum bearings. The experimental example assumes the experimental condition that includes very high contact pressure compared with contact pressure (about 10 to 20 MPa) generated in an actual use environment of internal combustion engines. Although the crests of the bearing alloy layer may be plastically deformed under the very high contact pressure, it is thought that the bearing alloy layer crest cannot be plastically deformed, as intended, under the actual general use environment (contact pressure about 10 to 20 MPa) when the bearing is applied to the internal combustion engine. Therefore, it is considered to be difficult to achieve the conformity within a short period of time under the actual general use environment.